7245 4 Wheel not working

Hi hello! I'm new to zetor world, any help would be appreciated. Iv had my 7245 about 5 years now it's been a great old tractor. So everything was fine I'm blowing snow 4 Wheel was working good. It got icey out so in a hurry I put chains on the front wheels only I would normally do all 4 Wheels. So as I'm blowing snow I start to realize the 4 Wheel is not working so I finished blowing snow. Now I've put on the back tire chains hoping maybe that would make a difference but no such luck. So was working fine and now not working at all. Lever is moving the linkage at the transfer case